<p>Subacute sclerosing panencephalitis (SSPE) and autoimmune encephalitis (AE) are distinct clinical entities, each characterized by unique management strategies and prognosis. SSPE represents a late sequela of persistent measles infection, with progressive cognitive decline, behavioral alterations, motor function deterioration and myoclonus. In contrast, AE is an inflammatory disorder of central nervous system, typically presenting with constellation of neurological and psychiatric symptoms. In pediatric AE, seizures, movement disorders, and focal neurological deficits are more prominent than behavioral manifestations. Although diagnosis of both conditions is based on well-established criteria, overlapping clinical presentations are frequently encountered. Furthermore, concurrent detection of both anti-measles immunoglobulin and N-methyl-D-aspartate receptor (NMDAR) antibodies in cerebrospinal fluid (CSF) further complicates diagnosis. The authors present two pediatric cases, each with differential diagnoses of SSPE and AE, both positive for CSF NMDAR and anti-measles antibodies. Given the contrasting management approaches and prognoses for these two conditions, it is essential to understand underlying pathophysiology and to identify potential masquerades preventing misdiagnosis.</p>